DA-02 · LESSON 04

UNIT transfer semantics

KEY DEFINITIONS

Terms used in this lesson

UNIT: Ducat’s dollar-pegged stablecoin, the asset a borrower can create against bitcoin collateral.
Runes: A Bitcoin metaprotocol that assigns fungible-token meaning to transaction outputs through off-chain interpretation.
Vault: A set of Bitcoin outputs and spending rules that holds collateral and represents the current loan state.
Collateral: An asset pledged against a debt; it can be used to cover the debt if agreed conditions are breached.
Runestone: Transaction data interpreted by the Runes protocol to describe token creation or allocation.
Cenotaph: A malformed or intentionally unrecognized Runes message whose affected token balances are burned under the protocol’s rules.
Outpoint: A transaction ID plus output number that identifies one exact prior output.
OP_RETURN: A Bitcoin Script operation commonly used to create an unspendable output carrying a small amount of data.
BTC: The common market ticker for bitcoin.

A UNIT transfer assigns token balances to transaction outputs under Rune indexing rules without by itself changing a Ducat vault's collateral or debt.

65 min Difficulty 4/5 Not started

VISUAL MODEL

See the whole mechanism before going step by step

Use the diagrams to orient yourself. Then the guided explanation below teaches every part in depth.

4 explanatory views

CONCEPT-SPECIFIC MAP · ducat vaultA Ducat action moves one Bitcoin-anchored vault state to a successorSelect any state to inspect its exact role.

RELATIONSHIP MAPInputs, rule, and outputs

01
PREDECESSORCurrent vault outpoint
The current Bitcoin output anchors collateral and identifies the state being spent.
02
REQUESTUNIT transfer semantics
The UNIT transfer semantics workflow proposes one exact action and successor state.
03
POLICYProfile, oracle, signatures
Applicable policy, price evidence, authorization, and transaction shape are checked.
04
BITCOIN SPENDScript-valid transaction
Bitcoin miners and nodes can include only a transaction that satisfies Bitcoin rules.
05
SUCCESSORNew outpoint and state
Ducat validators reconstruct debt, collateral, token, and account changes from the confirmed transaction.

Rule shown: Bitcoin checks the spend; Ducat components independently reconstruct and validate the additional protocol state.

STAGE 1 OF 5PREDECESSOR: Current vault outpoint

The current Bitcoin output anchors collateral and identifies the state being spent.

Governing relationship: Bitcoin checks the spend; Ducat components independently reconstruct and validate the additional protocol state. Complete path: 1. PREDECESSOR, Current vault outpoint. The current Bitcoin output anchors collateral and identifies the state being spent. 2. REQUEST, UNIT transfer semantics. The UNIT transfer semantics workflow proposes one exact action and successor state. 3. POLICY, Profile, oracle, signatures. Applicable policy, price evidence, authorization, and transaction shape are checked. 4. BITCOIN SPEND, Script-valid transaction. Bitcoin miners and nodes can include only a transaction that satisfies Bitcoin rules. 5. SUCCESSOR, New outpoint and state. Ducat validators reconstruct debt, collateral, token, and account changes from the confirmed transaction.

1. State transitionWhat exists, what changes, and what results

BEFORE

Outpoint X carries 120 UNIT and 12,000 sats. A separate wallet input supplies 3,000 sats. Recipient and change outputs carry 6,500 and 7,500 sats, leaving a 1,000-sat fee. Th…

MECHANISM

The wallet selects outpoints whose reconstructed Runes balances cover the transfer.

AFTER

The transaction conserves 120 UNIT as 45 + 75 and conserves bitcoin as 15,000 input sats = 14,000 output sats + 1,000 fee. No vault input means no debt change.

Text equivalent: Starting from Outpoint X carries 120 UNIT and 12,000 sats. A separate wallet input supplies 3,000 sats. Recipient and change outputs carry 6,500 and 7,500 sats, leaving a 1,000-sat fee. This vector differs from required practice. The mechanism begins when The wallet selects outpoints whose reconstructed Runes balances cover the transfer. The resulting lesson is The transaction conserves 120 UNIT as 45 + 75 and conserves bitcoin as 15,000 input sats = 14,000 output sats + 1,000 fee. No vault input means no debt change.

2. Mechanism pathSelect a stage to inspect its job

STAGE 1 OF 4

Select UNIT inputs

The wallet selects outpoints whose reconstructed Runes balances cover the transfer.

Complete path: 1. Select UNIT inputs: The wallet selects outpoints whose reconstructed Runes balances cover the transfer. 2. Build recipient and change outputs: The transaction creates Bitcoin outputs for the recipient and any token change. 3. Assign amounts by edict: Runestone instructions map the intended UNIT quantities to those output indexes. 4. Confirm and reconstruct: After confirmation, indexers consume the old token allocations and create the new ones.

3. Rule and failure boundaryWhat accepts the result and where it can stop

ACCEPTED PATH

The worked case executes the named inputs and checks in the displayed order. After confirmation, indexers consume the old token allocations and create the new ones.

CHANGED CONDITION

A missing, malformed, stale, unauthorized, or inconsistent required input stops at its first named boundary. Borrowing creates UNIT and debt. A later standalone transfer reallocates existing UNIT and does not create new debt.

Important distinction: Sending borrowed UNIT is another borrow action. Borrowing creates UNIT and debt. A later standalone transfer reallocates existing UNIT and does not create new debt.

Text equivalent: The accepted path is enforced by The worked case executes the named inputs and checks in the displayed order. After confirmation, indexers consume the old token allocations and create the new ones. If the required condition changes, A missing, malformed, stale, unauthorized, or inconsistent required input stops at its first named boundary. Borrowing creates UNIT and debt. A later standalone transfer reallocates existing UNIT and does not create new debt.

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Learn the idea

A UNIT transfer spends Bitcoin outputs carrying indexed UNIT balances and creates new outputs to which a runestone assigns those balances. The transfer changes token ownership, not the debt or collateral of a vault unless it is part of a separate Ducat action.

GUIDED EXPLANATION1/4 ideas inspected

Select UNIT inputs

The wallet selects outpoints whose reconstructed Runes balances cover the transfer.

The worked example follows the explanation

Inspect every idea above to open it.

Important distinction“Sending borrowed UNIT is another borrow action.”

Borrowing creates UNIT and debt. A later standalone transfer reallocates existing UNIT and does not create new debt.

FINISH LEARNING FIRST

The questions unlock after every required learning activity

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